Shielding system for vapor-converters.



L. W. CHUBBA SHIELDING SYSTEM FOR VAPOR CONVERTERS.

APPLlCATlON FlLED OCT. I. 1915.

1,281,518. Patented Oct. 15, 1918.

2 SHEETS-SHEET I.

WITNE SES: 7 INVENTOR L e Wl$ W Chubb.

L. W. CHUBB.

SHIELDING SYSTEM FOR VAPOR CONVERTERS. APPLICATION FILED 0e17, \915.

. 1,281,518. J Patented Oct-b 15, 1918.

2 SHEETS-SHEET 2.

WITNESSES: INVENTOR Lew/s W Chubb.

UNITED sTA'rEs PATENT .oFFron.

LEWIS W. CHUIBB, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTINGIiOUSE "ELECTBIC AND MANOFAC'IURING COMPANY, A CORPORATION OF PENNSYLVANIA,

SH-IEL DING. SYSTEM FOR VAPOR-CONVERTERS.

Tdall whom it may 60mm.-

Be it known that I, Lnwrs W. CH'UBB, a

' citizen of the United States, 'and'a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Im rovement in Shielding Systems'for Vaporonverters, of which the following is a specification.

My invention relates to shielding systems for vapor converters, and it has for its object to provide means and apparatus whereby thepower arc in apparatus of the char acter specified may be properly directed and controlled and whereby-short circuiting, rc-' verse arcing and other harmful phenomen: may be minimized.

In the accompanying drawings, Figure 1 is a side view, partially in section and partially in elevation, of a vapor converter of the metal-case type, together with attendant supply and control circuits, illustrating one embodiment, of my invention; Fig. 2 is a diagram illustrating the relation of the voltage waves in thevarious component parts of'the system shown in Fig. 1; Figs. 3, 5 and 7 illustrate various modifications in the system and apparatus shown in Fig. 1; and Figs. 4, 6 and 8, respectively, are diagrams similar to Fig. 2 and illustrating the voltage waves in the accompanying systems.

In theoperation of vapor converters and similar evactuated electrical apparatus, current is conveyed between the electrodes by a stream of electrons, emitted b i the cathode and proceeding to the anode. he stream of electronsat the cathode may be excited by any of several well known methods, chief among which are the maintenance 'of a keepalive arc to the cathpde, .the maintenance of the cathode at incandscence, the impact :of

a stream ofipositive ions therea ainst, and

the impact 0 a beam of ultra-vio et light.

If, in its passage from the cathode to an anode, an electron collides with a particle of residual gas, the particle is broken up into positive and negative ions, both of which receige an initialimpulse toward the anode by "the impact. The newly freed electron moves on, very rapidly because the propel-' ling force of the electrostatic-field 1sv substantially coincident .in direction with the initial impulse thus given, but the newly freed' positive ion moves but slowly and may soon come to rest and even reverse its direction of movement because of the -neutral-- Specification of Letters Patent.

Patented Oct. 15, 1518.

the initial impulse. Furthermore, the acceleration tending to'be imparted to the positive ions by the electrostatic field is much less than that of the electrons because of the vastly larger mass of the former, even though it carry an equal or greater charge. The initial velocity of a gas mole cule at the instant of ionization, or other force, may carry the resultant positive ion transversely to the arc path and into a part of the electrostatic field where it Will be drawn to the inactive anode (having a nega tive potential) rather than to the cathode. The initial velocity and that imparted by the electrostatic field may be sufficient to cause a cathode spot when the ion strikes the inactive anode, releasinga stream of elec trons and resulting in a short circuit or reverse arcing.

The sudden passage of an anode to a condition of negative polarity with respect to the-cathode, such as happens periodically in a vapor converter, finds a large number of free positive electrons afloat in and near the arc path without any well defined motion in any direction. These tramp ions are now attracted to the temporarily negative anode and if in sufficient number and sufficiently accelerated, they may also bombard the elec- Y cury or'other foreign matter upon the electrode surface.

In copending applications of S. W. Farnsworth Serial No. M329, filed Aug. 9, 1915, and Charles LeG, Fortescue, Serial No. 44,428, filed Aug. 9, 19l5,-both of which are assigned to the Westinghouse Electric & Manufacturing Company, are disclosed systems wherein a conducting shield is mounted in proximity to each anode-and is connected to changeain polarity therewith' so that,

. -when an anode becomes. negative in potential, its attendant shieldalso becomes negative and tends,to'collapse the neighboring positive tramp ions. At the instant when an-anodeis reversing in polarity with respect to the cathode, the number of positive trampions in its arc ath is near orat a maximum. It would e desirable to have the ion sup ressing means of maximum ac-' mum activity of the suppressing devices is not reached until ninetyelectrical degrees later. By my invention,I provide means whereby the relation of the instant of maximum activity of a suppressor shield may be accurately timed with respect to the instant of maximum undesirable positive ionization in the associated arc path, thus greatly increasing the effectiveness of operation ofa device of the character described;

Referring to the accompanying drawing for a more detailed understanding of my invention, I show the container of a vapor converter of the metal-case type at 9 in Fig. 1. The container 9 is provided with solid anodes 10 and 11 and with a cathode 12, preferably composed of a vaporizable reconstructing material, such, for example, as mercuryor suitable amalgams. The anodes 10 and 11 are connected,.respectively, to the terminals of a source of alternating current 13, and the cathode 12 is connected to the mid-point of the source 13 through a load 14, as is com- .mon in rectifier systems. The cathode 12 may be maintained in an active condition by any suitable means, such, for example, as a keep-alive circuit 15. A shield 16 of any desired type is provided for each of the anodes 10 and 11 in order to minimize short.

circuiting. A plate 17, formed of conducting material, is mounted between the anodes 10 and 11 and is connected to the cathode 12 through a current-limiting device 18, a synchronous'ly operating contact making device 19 and a potential source 20.

Having thus described the arrangement of the elements in Fig. 1, the operation is as follows: upon starting the device into operation,.the anodes 10 and 11 rapidly alternate in potential with respect to each other between a point slightly above the potential of the cathode and a potential c'onslderably below the same reference voltage. This is shown clearly in Fig. 2 wherein a reference line 21-21irepresentsthe potential of the cathode12, a line 22-22 represents the potential of the anode 10 and a line 23-23 represents the potential of the anode 11. The lines 22 and 23 rise but little above the lines 21-21 because an anode, when positive and active, differs from the cathode in potential only by the drop through the arc path, said drop being maintained at a minimum amount in the interests of efiiciency. The lines 22 and 23, however, dropv to a considerable distance below the line 21-21, as an anode, when. negative, assumes a potential below that of the cathode by an amount de termined by the load drop or substantially one-half the total impressed electromotive force of the transformer winding.

With each successive current impulse from contact device 19 that the plate 17 is stron "from the source 20 during each instant when the arc is being transferred from one anode an anode through a cathode, the arc path formed thereby becomes more or less saturated with positive tramp ions, and it is deto another. The presence of a negatively charged conducting body in the near vicinit of an arc path immediately attracts and co lapses substantially all of the harmful positive ions and thus insures reliable operation. The potential of the shield 17 is shown by a line 25-25 in Fig. 2, said line clearly indicating that the member 17 is at a maximum negative potential when the anodes 10 and 17 are passing through a point-of zero potential with respect to the cathode.

It may frequently be desirable to maintain a negative suppressing member associated with an anodein a condition of negative potential during the time when the associated anode is positive in potential and therefore active, thus providing means for collapsing the positive tramp ions as generated. .It is impossible to arrange a system of this character wherein a single suppressing apparatus affects both anodes, as is shown in Fig. 1, and I, therefore, provide a separate suppressing device for each anode, as shown in Fig. 3. A converter. of the general type shown in Fig. 1, is provided with two conducting plates 26 and 27 associated, respectively, with the anodes 10 and 11, and the plates 26 and 27 are rovided, at their lower portions, with latera 1y extending proj ectin screen members 28 and 29 for extendirig t e effects of the suppressing fields throughout the arc paths. The COIltilCtflnBking device 19 is so arranged that the shield 26-28 is negatively charged soon after the negatively charged, as, otherwise, electrons from the cathode cannot reach the anode, and the converter operate with diflicultyq. The phasial position of the lines 30 and 31 is therefore somewhat retarded with respect -to--that of the.lines and 23-23, as

shown in 'Fig:"'4.

The point of attachment of ,the cathode 12 to the source 20 may be varied so that the maximum potential im arted to the suppressing members may adjusted to such an amount as to suppress practically all the undesirable ions without exerting too strong a repulsive action upon the negative electron stream proceeding from the cathode to the anode and constituting the power a r itself.

If desired, by proper adjustment of the contacting device 19, the shielding members 26-28 and 2729 may be rendered negative when their associated anodes are negative,

' thus producing an action similar to that indicated in the above mentioned applications of Farnsworth and Fortescue with the exception that the suppressing 'action is some- What more pronounced in'my device because the potential waves 30 and 31 are square-top in form, thus producing a strong suppressing' charge on the shield member in an extremely short period of time after the associated anode has become inactive.

I The operation of a contact-making device of the type indicated at 19 is frequently more or less unsatisfactory because of the difficulty of maintaining a predetermined phase relation exactly with an synchronous motor now known. I may therefore avail myself of the well known monocyclic square to obtain the desired displaced electromotive force for the energization of the suppressor at any desired value with respect to the cathode 12. By suitable adjustment of the electrical constants of the monocyclic square, any desired phase displacement may be obtained for the members 32 and 33, and thepotential v, thereof may be adjusted by a transformer 38.

A desirable arrangement of volta e waves in the system of Fig. 5 is indicate in Fig. 6, wherein the otentials-of the anodeslO and 11 are indicated by lines 22-22 and 2323 and wherein the tentials'of the members 32 and '33 are'1ndicated respectivelya'by lines 39-39 and 40-40, reaching a maximum negative value when the correg ending anode ceases activity. YStill another method oi-energ zm sup- ' pressing shields is shown in Fig; 7 w erein an im ulse transformer 42-is provided, said trans ormer com risinga core member 43 provided with a eakage path 44 and a leg said member at the conclusion 0 'tive period of the electrode,

associated anode.

45 of small cross section, 'Iwo opposing primary windings 46-46 are mounted on the core member 43 and inserted respectively in the connections to the anodes 10 and 11 of a vapor converter 9. A single secondary winding 47 is mounted on the constricted leg =45 and its terminals are connected respectively to suppressor members 48 and 49 associated with the anodes l0 and 11. The

1 mid point of'the secondary winding 47 is connected to the cathode 12 through a current-limiting device 18.

In operation, the abrupt flux change in the restricted leg 45 at the beginning and end of saturation produces a momentary voltagewave or impulse of great intensity, as is well known in the art. .Bythe proper connection, saidimpulses may be made use of in charging the suppressor members 48 and 49 in any desired manner. In the diaram of Fig. 8, the potential of the shield 48 is indicated by a line 50,5O and that of the shield 49 by a line 51-51.

Throughout this description, I have ex- I plained the action of my device in accordance with the theory which seems most plausible inview of the present knowledge of the underlying phenomena. I desire it to be distinctly understood,.however, that I do not confine myself to said theory of operation but merely present the same to aid in an understanding of the case.

While I have shown my invention 1n its f referred form, it will be obvious to those killed in the art that it is susceptible ofyarious minor changes and modifications without departin from the spirit thereof and I desire, there ore, that only such limitations shall be "laced thereupon as are imposed by the prior art or are specifically set forth in the appended claims. 7 a

I claim as my invention:

1. In a vacuum-type converter, means for providing an arcpath which is intermittently active, a conducting member associated with said are path, and means for negatively charging said member at the conclusion of each active period.

2. In a vacuum-type converter, the come bination with an e ectrode which is alternately ositive and negative in polarity, of a con ucting' member mounted ad acent thereto, and means fornegativel chargmg each posi- 3.'In a vacuum-type converter, the commeans for causing a power are to operate successively, fromeach of sa1d anodes, a conducting. member assoc ated with each of the arc paths thus determined, and 'means' for temporaril imparting] a anodes,

.negative charge to each con ucting member at the conclusion of an active period of the bination with a cathode, of a plurality of 4. In a vacuum-type converter, the combination with a cathode, of two anodes,

means for causing said anodes to alternately pass from positive to negative potential with respect to said cathode and for a power arc to flow therefrom to said cathode when positive with respect thereto, a conducting member associated with each arc path thus determined, and means for momentarily imparting a negative char e to each conductmg member at the cone usion of an active period of the associated anode.

' 5. In a vacuum-type converter, the combination with a cathode, of two anodes,

member associated with each means for causing said anodes to alternately pass from positive. to negative potential with respect to said cathode and for a power are to fiow therefrom to said cathode when positive with respect thereto, .a conducting arc path thus impressing al- 11 each of said members which. lead the e ectromodetermined, and means for tiveforce of the associated anode by substantially ninety electrical degrees.

6.In a vacuume converter, the combination with a cat ode, .of two anodes,

means for causing said anodes to alternately pass from positive to negative potential with respect to said cathode and for a war are to flow therefrom to said cathode when positive with resgct conducting mem rarc path thus determined, and means for impressing alternating clectromotive forces upon each of said members which lead the electromotive force of the associated anode by substantially ninety electrical degrees.

7 In a vacuum-type converter system,- the combination with a cathode, of a plurality of anodes, means for applying an alternating electromotive force between said electrodes, and means for imparting a ulsating electromotive force of doubleequency to the interior of said container intermediate said anodes, said double-frequency electromotive force having its 11 tive crests displaced by substantially with respect to the electromotive force applied. to said electrodes.

Intestimony whereof, I have hereunto subscribed my name this 28th day of Sept,

LEWIS W. CHUBB.

thereto, a perforated mounted across each 

